LIFETIME OF LIVING POLYMERS IN CATIONIC POLYMERIZATION .1. METHODOLOGY AND APPLICATION TO THE HI/I-2-INITIATED LIVING CATIONIC POLYMERIZATION

An end-capping method using sodiomalonic ester (1) as a quencher was shown to permit the determination of the concentration ([P*]) of living ends in the polymerization of isobutyl vinyl ether initiated by the hydrogen iodide/iodine (HI/I2) system in toluene or methylene chloride at 0 to -40 °C. The terminal malonate group, thus attached to the polymer chain, could be determined by NMR spectroscopy, from the concentration of which [P*] was obtained. Throughout the polymerizations, the living-end concentration remained constant against monomer conversion and equal to the initial concentration of hydrogen iodide ([P*] = [HI]0), and the same relation held for the second-stage polymerizations that were started by adding a fresh feed of monomer to completely polymerized reaction mixtures. After the complete consumption of the monomer, however, the living end turned out to decay progressively with time, in first order with respect to [P*], and by following this decay its lifetime could be determined. The half-life of the living end, even in the absence of monomer, was relatively long, ranging from 40 to 1000 min (17 h). The decay process was slower at lower temperature but accelerated at higher iodine concentrations. © 1990, American Chemical Society. All rights reserved.